THE WING. 19 



quadruped. The convexity of the wrist-joint, or car- 

 pus, looks forward, as that of the ankle-joint does back- 

 ward ; and being the most prominent bend in the limb 

 away from the body, is sometimes very wrongly called 

 the "shoulder." But the shoulder-joint of a bird is 

 found high up, buried in the muscles of the breast ; the 

 first bend in the limb has its convexity directed back- 

 ward, and corresponds to our elbow. The wing is 

 clothed with ordinary feathers, like those of the body, 

 but has in addition the large stiff quills, which make 

 up the greater part of the expanse of the wing. These 

 quills, usually nine or ten in number, which grow upon 

 the pinion-bones, that is, upon the bones of the hand 

 and fingers, beyond the wrist, are called the -primaries. 

 Those which are situated upon the ulna, one of the 

 two bones between the wrist and elbow, are called sec- 

 ondaries. A few of the innermost of these, or a row 

 of such feathers above the elbow, are often described 

 as the tertiarics. The bases of these large feathers 

 are protected by several rows of coverts, as they are 

 called, the special arrangement of which sometimes 

 affords good characters for classification. 



The bones of a bird's hand, like those of the tarsus, 

 are originally distinct, but soon fuse together. The 

 number of digits, or fingers, which remain separate is 

 normally two or three ; the outermost of which, com- 

 monly called the "thumb," bears the set of feathers 

 known as the alula, or " bastard wing." 



In case the first primary of a bird is rudimentary, or 

 very much shorter than the second, it is commonly 

 said to be spurious. The first and largest row of wing- 

 coverts, overlying the secondary quills, are the greater 

 coverts; the next row are the median coverts; the 



